Cutter guide for pipe perforating machine

ABSTRACT

In a pipe perforating machine including a cutter head movable through a pipe and cooperating with shear blades carried by the machine frame, a cutter guide consisting of guide ways extending through the pipe and on which the cutter head is slidably mounted, a fixed support for one end of the guide ways, a movable support for the free other end of the guide ways which is detachable from the ways to permit the pipe to be threaded longitudinally over the ways, a fixture detachably mountable on the guide ways at the free end thereof and including a roller on an axis transverse to the pipe and engageable with the frame to support the free ends of the ways when said movable support is disengaged, while still permitting the threading of the pipe over the ways, the cutter head including a toothed cutter wheel and being movable outwardly from the end of the pipe, and a fixture carried by the frame and urged against the end of the pipe, and operable to catch and secure the cutter wheel against rotation as it emerges from the pipe, whereby when it re-enters the pipe, its teeth will always begin cutting perforations at the same distance from the end of the pipe.

United States Patent [1 1 Foulks et al.

[ CUTTER GUIDE FOR PIPE PERFORATING MACHINE [76] Inventors: Noah E. Foulks; Earl Lowry, both of Rt. No. 1, Dodge City, Kans. 67801 22 Filed: Sept. 20, 1972 211 Appl. No.: 290,578

[52] US. Cl. 72/71, 72/113 [51] Int. Cl B2ld 28/28 [58] Field of Search 72/71, 113; 29/1635 R {56] References Cited UNITED STATES PATENTS 3,l56,285 l 1/1964 Layne 72/71 3,678,718 7/l972 Brown et all .1 72/7! Primary Examiner-Lowell A. Larson Attorney-John A. Hamilton [57] ABSTRACT In a pipe perforating machine including a cutter head movable through a pipe and cooperating with shear blades carried by the machine frame, a cutter guide consisting of guide ways extending through the pipe and on which the cutter head is slidably mounted, a fixed support for one end of the guide ways, a movable support for the free other end of the guide ways which is detachable from the ways to permit the pipe to be threaded longitudinally over the ways, a fixture detachably mountable on the guide ways at the free end thereof and including a roller on an axis transverse to the pipe and engageable with the frame to support the free ends of the ways when said movable support is disengaged, while still permitting the threading of the pipe over the ways, the cutter head including a toothed cutter wheel and being movable outwardly from the end of the pipe, and a fixture carried by the frame and urged against the end of the pipe, and operable to catch and secure the cutter wheel against rotation as it emerges from the pipe, whereby when it re-enters the pipe, its teeth will always begin cutting perforations at the same distance from the end of the pipe.

10 Claims, 12 Drawing Figures PATENTEDJAH 1 I974 SHEET 10F &

CUTTER GUIDE FOR PIPE PERFORATING MACHINE This invention relates to new and useful improvements in pipe perforating machines, and has particular reference to improvements in the pipe perforating machine shown and described in US. Pat. No. 3,678,718, issued July 25, 1972. Reference may be had to said prior patent for any details of structure and operation not shown herein.

In the above identified prior patent, there is shown a pipe perforating machine in which a cutter head is drawn into and through a pipe, said cutter head including a pair of cutter wheels rotatable about axes transverse to the pipe and engaging the interior wall of the pipe along diametrically opposite lines, each cutter wheel having radially projecting, angularly spaced teeth which cooperate with a pair of shear blades extending longitudinally along the outer surface of the pipe to perforate the pipe, each tooth forming a pair of parallel longitudinal slits in the pipe wall, and offsetting the strip of pipe wall between the slits outwardly by a distance greater than the wall thickness. The pipe may be angularly indexed after each pass of the cutter head, successively, until the entire pipe wall area is perforated.

It will be apparent that for efficient operation of the cutter head, it must be rigidly supported and guided during its passage through the pipe. The prior patent shows a cutter head support and guide consisting of long guide ways extending longitudinally through the pipe and outwardly from both ends thereof, a fixed rigid support from the machine frame for one end of said ways, and a support for the other end of the ways, the latter being removable to permit the pipe to be threaded longitudinally over the ways. This type of support is adequate during the actual perforating operation, but is deficient during certain intermediate steps of the process, such for example during the times pipes are being inserted into or removed from the machine, and when the cutter wheels are moved outwardly from the end of the pipe, as they must be between successive passes thereof through the pipe.

When a pipe is to be inserted or removed, the removable support at one end'of the guide ways must be removed. This constitutes the ways as a cantilever beam, supported at only one end, and due to the length thereof, often -25 feet, the free end thereof sags downwardly to such an extent as to drag heavily on the bottom inner wall of the pipe, making the removal of a pipe, or the insertion of a new one, quite difficult. An important object of the present invention, therefore, is the provision of an auxiliary fixture which may be attached to the free end of the guide ways, preparatory to the disengagement of the removable support, which functions to prevent sagging of the free ends of the guide ways, but which nevertheless leaves the ways accessible for eacy insertion or removal of a pipe.

Also, when the cutter head is moved outwardly from the pipe end after each pass of said cutter head, so that the pipe can be angularly indexed for the next pass, the cutter wheels thereof are free, and often turn more or less at random, so that when they re-enter the pipe,

they may be angularly indexed differently than when I they emerged. This may cause the perforating slits cut by the teeth to extend through the extreme end of the pipe, which is a highly undesirable condition since it leaves sharp-ended strips of metal between the slits angling outwardly from the pipe. This condition has heretofore necessitated manual indexing of the cutter wheels just before they enter the pipe. Another important object of the present invention, therefore, is the provision of an auxiliary fixture carried by the frame and operable to arrest and secure the cutter wheels against rotation as they emerge from the pipe, and to release them as they re-enter the pipe. The fixture thus insures that each pass of the cutter head will begin with the cutter wheels identically indexed, and it may be pre-set to insure that the first perforation of each pass will be spaced inwardly apart from the end of the pipe.

Other objects are simplicity and economy of construction, and efficiency and dependability of operation.

With these objects in view, as well as other objects which will appear in the course of the specification, reference will be had to the accompanying drawing, wherein:

FIG. 1 is a longitudinal vertical sectional view, partially broken away and foreshortened, of a pipe perforating machine including a portion of the cutter guide means contemplated by the present invention, with the parts shown at an intermediate stage of the insertion of a pipe to be perforated,

FIG. 2 is a sectional view taken on line II-Il of FIG.

FIG. 3 is a fragmentary sectional view taken on line III-III of FIG. 1,

FIG. 4 is a top plan view of the cutter head and related parts in the position shown in FIG. 1,

FIG. 5 is a sectional view taken on line V-V of FIG.

FIG. 6 is a sectional view taken on line VI-VI of FIG. 1,

FIG. 7 is an enlarged fragmentary view similar to FIG. 1, showing the guide way support fixture operatively mounted at the free end of the guide ways, and with a pipe being inserted into the machine,

FIG. 8 is a fragmentary sectional view taken on line VIII-VIII of FIG. 7,

FIG. 9 is an enlarged, fragmentary sectional view similar to FIG. 1, showing the cutter wheels as they emerge from the pipe, and including a cutter wheel arresting fixture as contemplated by the present invention, just prior to full engagement of the arresting fixture,

FIG. 10 is an enlarged fragmentary view similar to FIG. 9, showing the arresting fixture in full engagement,

FIG. 11 is a sectional view taken on line XI-XI of FIG. 9, and

FIG. 12 is a reduced sectional view taken on line XII- -XII of FIG. 9.

Like reference numerals apply to similar parts throughout the several views, and the numeral 2 applies generally to the main frame of the machine. Said main frame includes a pair of parallel, spaced apart l-beams 4 extending the full length of the machine and securely affixed to the floor 6 by any suitable means. The right end of the machine as viewed in FIG. 1, may be termed its forward end and is the end from which a pipe 8 to be perforated is inserted and removed. A series of cross bars 10, also constituting l-beams, extend horizontally and transversely across I-beams 4, and are welded or otherwise securely affixed thereto. Carried by each of certain of cross bars 10 is a bridge member indicated generally by the numeral 12, constituting a pair of vertical posts 14 securely affixed at their lower ends to the respective ends of a cross bar 10, said posts extending upwardly and being rigidly connected at their upper ends by a horizontal, transversely extending cross bar 16. Only one bridge 12 is shown, but it will be understood that there may be additional bridges, spaced along the length of the machine as required, and that successive bridges may be braced by horizontal stringers 18 extending therebetween longitudinally of the machine. An elongated lower rail 20, of great strength and rigidity to resist flexure thereof, extends along the midline of the machine, being supported on cross bars and welded or otherwise rigidly affixed thereto. It is of rectangular cross sectional contour with its major axis arranged vertically, and a pair of parallel shear blades 22, spaced apart by a spacer plate 24, are set in the upper edge of said rail, being secured therein by rivets 26. Said blades project above rail 20 and spacer plate 24, and extend nearly the full length of said rail.

A top rail 28 corresponding to lower rail 20, and carrying corresponding shear blades 22 and spacer plate 24 mounted in the lower edge thereof, is disposed above and parallel to said lower rail, said upper rail also being of greater length than pipe 8, but somewhat less than the length of lower rail 20. Said upper rail is affixed to an auxiliary frame designated generally by the numeral 30, and consisting of a horizontal bar 32 extending the full length of rail 28, and to the lower surface of which said rail is welded or otherwise affixed, and a series of cross beams 34 of box form welded to and extending horizontally and transversely from opposite sides of rail 28. Cross beams 34 are arranged in aligned pairs at opposite sides of rail 28, each pair (one shown) being aligned with one of bridges l2 and disposed directly beneath cross bar l6 of said bridge member. The outer ends of beams 34 at each side of the rail may be connected by stringer beams 36 extending therebetween longitudinally of the machine and welded thereto.

Auxiliary frame 30 is supported, guided and powered for vertical movement by means best shown in FIG. 6, which shows the means provided for these purposes at the single bridge member 12 shown, although it will be understood that similar means are provided at each bridge member actually used. At each side of pipe 8, there is disposed a vertical post 38 affixed at its lower end to the associated l-beam cross bar 10, and at its upper end to the cross bar 16 of the bridge member. A pair of sleeves 40 fixed in the cross bars 34 of the auxiliary frame 30 at that bridge are respectively slidably mounted on the two posts 38, whereby said posts guide ssid auxiliary frame in its vertical movement. At each side of pipe 8, there is also disposed a vertical hydraulic ram, the cylinder 42 of said ram being connected at its lower end, as at 44, to cross bar 10, and the upper end of the piston rod 46 thereof being secured, as at 48, to the associated cross bar 34 of the auxiliary frame. Each of cylinders 42 is double-acting, having a top inlet 50 for hydraulic fluid whereby the ram is shortened to lower the auxiliary frame, and a bottom inlet 52 for hydraulic fluid whereby the ram is lengthened to raise the auxiliary frame. All of cylinders 42 receive hydraulic fluid from a common source, the pumping and valving arrangement being standard and not here shown.

To insure that auxiliary frame 30 is level, and that shear blades 22 carried by the upper rail are parallel with those of the lower rail, when the auxiliary frame is lowered to grip the pipe between said upper and lower sets of shear blades, there is also provided at each side of said pipe a vertical post 54 fixed at its lower end to cross bar 10, and having inserted in its tubular upper end an adjusting screw 56 on which is threaded a heavy nut 58 abutting the top of the post. When the upward projection of said screws is properly adjusted, they are engaged by cross bars 34 when auxiliary frame 28 is lowered to grip pipe 8 between the upper and lower shear blades. This insures parallelism of the shear blades despite any slight inequality in the rates of movement of the hydraulic rams, and also permits a slight flattening of the pipe to insure full line contact of the blades with the pipe despite irregularities of the pipe itself.

A hanger 60 of inverted U-form is carried by auxiliary frame 30 adjacent front bridge member 12 so as to bridge the forward end portion of pipe 8, and it will be understood that said auxiliary frame carries a similar hanger adjacent the rearward end of the pipe. As best shown in FIG. 2, each hanger 60 includes a top cross bar 62 extending transversely over the top bar 34 of the auxiliary frame, and welded thereto, and a pair of legs 64 depending from the ends of said cross bar, respectively at opposite sides of pipe 8, to the level of cross bars 10 of the main frame, where they are connected by a tie bolt 66 extending transversely beneath lower rail 20, whereby to prevent spreading of their lower ends. A pipe guide 68 is mounted slidably on each of legs 64, and is fixed thereon by a set screw 70. These guides prevent the pipe from rolling laterally off of shear blades 22 of the lower rail during certain stages of the operation, as will appear. Also mounted on each leg 64, and fixed thereon by a set screw 72, is a slide 74 carrying a roller wheel 76 for rotation on an axis parallel to the pipe, said wheels being disposed inwardly of legs 64 so as to lie beneath the pipe. Roller wheels 76 support the pipe for axial rotation during certain stages of the operation, as will appear.

Since pipe 8 is inserted longitudinally into the machine from the forward end thereof, and also removed in a forward direction, rollers are needed for supporting the pipe during these movements. For this purpose, there are provided at intervals along the length of lower rail 20 a series of pairs of roller wheels 78 (one pair shown) as shown in FIGS. 1 and 2, the wheels of each pair being disposed respectively at opposite sides of rail 20, beneath pipe 8, and with their axes transverse to said pipe. Each roller wheel 78 is carried at the upper end of an arm 80 extending downwardly and pivoted at its lower end, as at 82, to a bracket 84 affixed to one of I-beams 4 of the main frame. A link 86 is pivoted, as at 88, to each of arms 80 in spaced relation above pivot 82, and extends downwardly and forwardly. The lower end of each of links 86 is pivoted, as at 90, to an elongated bar 92, extending longitudinally of the machine beneath cross bars 10, of the main frame. The forward end of bar 92 is affixed to the piston rod 94 of a hydraulic cylinder 96 mounted on the main frame by bracket 98. Cylinder 96 is double-acting, whereby bar 92 may be moved either forwardly or rearwardly, and is furnished with the hydraulic fluid when desired by standard means, not shown. When bar 92 is moved rearwardly, roller wheels 78 take the positions shown in dotted lines in FIG. 1, being lowered sufficiently to allow pipe 8 to rest on lower shear blades 22. When bar 92 is moved forwardly by cylinder 96, wheels 78 are raised as shown in solid lines in FIG. 1, and in FIG. 2 to support pipe 8 above the blades 22 of lower rail 20 for longitudinal rolling movement. It will be understood that bar 92 operates all pairs of roller wheels 78 which may be used.

A cutter head 100, to be more fully described below, is supported for movement through the pipe by a pair of guide ways 102 extending through the pipe and outwardly from-the ends thereof. Each of said ways constitutes an elongated plate disposed in a vertical plane, and they are spaced laterally apart, each being reinforced by a rib 104 affixed to its outer surface. At their rearward ends, each way is permanently and rigidly affixed to a vertical post 106 which is affixed at its lower end to the rearward end of rail 20. Posts 106 are disposed outwardly of ways 102, extend above said ways, and are connected adjacent their upper ends by a tie bolt 108 to prevent spreading thereof.

During actual perforation, the forward ends of ways 102 are each supported by a post 110, said posts being coaxially pivoted at their lower ends to the opposite sides of rail 20, as at 112, and being rigidly connected by a cross bar 114 extending past the forward end of rail 20 to form in effect a single compound post 116. Posts 110 extend upwardly past the distal sides of ways 102, as best shown in FIG. 5, each having an outwardly projecting pin 118 fixed therein adjacent its upper end to underlie and support an ear 120 affixed to the outer surface of the associated way, whereby to support said way. However, said posts may be pivoted downwardly and forwardly, as shown in dotted lines in FIG. 1, to permit the threading of a pipe over the ways. Said posts may be pivoted between their raised and lowered positions by a hydraulic ram 122 (see FIG. 1) pivoted at one end to a cross bar of the main frame, as at 124, and pivoted at its opposite end, as at 126, to a cross pin 128 extending between said posts below rail 20.

There is provided a carrier 130 for cutter head 100 at the forward end of ways 102. As best shown in FIG. 4, said carrier includes a pair of ways 132 forming forward extensions of ways 102, ways 132 being long enough to support head 100 thereon, and being rigidly connected by an end plate 134 at their forward ends. Said carrier is supported by a lateral arm 136 affixed at its outer end to a sleeve 138 rotatably mounted on a vertical post 140 affixed at its lower end to one of I- beams 4 of the main frame. By means of arm 136, carrier 130 may be moved to the solid line position of FIG. 4 wherein its ways 132 abut the forward ends of ways 102 to form forward extensions thereof, and may be secured in this position by any suitable means, such as a hook 142 pivoted thereto at 144 and engageable with a pin 146 fixed to one of the ears 120 of ways 102, or may be pivoted to'one side, as shown in dotted lines in FIG. 4, whereby to leave the forward ends of ways 102 unobstructed for the insertion or removal of a pipe 8, as will appear.

Cutter head 100 comprises essentially a solid block engaged slidably between ways 102, or ways 132, and has guides 148 slidably engaging both the upper and lower edges of said ways. A pair of cutter wheels 150 are mounted rotatably in the head, respectively above and below each other adjacent the forward end of the head, by means of axles 152 engaged in said head. Each cutter wheel includes a series of angularly spaced, radially projecting teeth 154. Each tooth has a length, an-

gularly of the wheel, corresponding to the length of the pipe perforation desired. Each tooth is transversely square, and its ends are rounded about axes parallel to the wheel axis. The cutter wheels are vertically spaced apart at such a distance that they roll respectively along diametrically opposite longitudinal lines of the interior surface of pipe 8 when said pipe is clamped between upper and lower shear blades 22 and the cutter head is moved through the pipe. Cutter teeth 54 are transversely aligned with the spaces between the pairs of shear blades. The radial projection of teeth 154 from the wheel peripheries is greater than the wall thickness of the pipe, so that as the cutter head is moved through the pipe, each tooth 154 cooperates with the associated shear blades 22 to cut a pair of parallel slits in the pipe wall, and to offset the strip 156 of wall metal between said slits outwardly into the groove between the shear blades, as best shown in FIGS. 9 and 10. Since the off set thus obtained is greater than the pipe wall thickness, this opens narrow slots 158 between strips 156 and the undisturbed portions of the pipe wall. The cutter head also carries a pair of smooth roller wheels 160 for axial rotation, each wheel being spaced rearwardly of one of cutter wheels 150, and adapted to roll against the interior surface of the pipe as the head is moved therethrough. Wheels 160, in conjunction with cutter wheels 150, provided a four-point support for the cutter head as it moves through the pipe, to prevent any possible rocking of the head about a horizontal transverse axis.

Cutter head is provided with rearwardly projecting ears 162, between the guide ways, said ears being releasably joined by means of a removable vertical pin 164, to the forwardly projecting ear 166 of a support head 168 also having guides 170 (see FIG. 5) supporting it for sliding movement along ways 102. Support head 168 is affixed as by rivet 172, to the forward end of a heavy pull beam 174, which extends longitudinally of the machine between the guide ways. Said pull beam is of such length that even when cutter head 100 is positioned on carrier 130, said pull beam extends rearwardly from the rearward ends of guide ways 102. Said pull beam may be moved axially, in either direction, by any suitable power means, not shown herein, although a suitable means is illustrated and described in the aforementioned prior patent.

To ready the machine for the insertion of a pipe 8, cutter head 100 is moved forwardly by beam 174 until it is supported entirely by carrier as shown in FIGS. 1 and 4, while support head 168 is still engaged on guide ways 102. Then pin 164 is removed, hook 142 is released, and carrier 130 is pivoted to one side as shown in dotted lines in FIG. 4. Also, roller wheels 78 are elevated to the position shown in FIG. 2, and in solid lines in FIG. 1, by operation of hydraulic cylinder 96, and auxiliary frame 30 is elevated by operation of cylinders 42 to the position shown in FIGS. 1, 2, and 6, with upper rail 28 spaced above lower rail 20 by a distance greater than the pipe diameter, but not so high that wheels 76 carried by hangers 60 will engage a pipe 8 supported by wheels 78.

The next step would be to operate hydraulic rams 122 to lower post 116 to the position shown in FIG. 7, and in dotted lines in FIG. 1, since this would clear the forward ends of ways 102 'for the insertion of a pipe. However, due to the great length of ways 102, and the flexibility of even the best steel, the forward ends of said ways would sag to rest on lower rail when the support of post 116 is removed, making the insertion of the pipe extremely difficult, if some auxiliary support were not provided. This auxiliary support is provided by a special fixture 176 shown in FIGS. 7 and 8, and forming one of the two principal features of the present invention.

Fixture 176 includes a bracket 178 of inverted U- form adapted to be inserted between the forward ends of ways 102 as shown, said bracket having out-turned lips 180 at the lower edges of its legs to engage the lower edges of ways 102, a clamp plate 182 overlying the upper edges of said ways, a screw 184 fixed in the upper end of bracket 178 and extending upwardly through the clamp plate, and a nut 186 threaded on said screw above the clamp plate. Bracket 178 carries a rotatable wheel 188 on a horizontal axle 190 transverse to the ways. The bracket is provided with a handle 192 whereby it may be easily inserted between the ways, and clamped in place by tightening nut 186. The fixture also includes a smaller roller 194, disposed directly beneath wheel 188, supported by a stub axle 196 which rests removably in notches 198 formed in the upper edge of lower rail 20 (see FIG. 1).

After fixture 176, including roller 194, has been inserted as shown, post 116 may be lowered by operation of ram 122, leaving the forward ends of ways 102 fully supported by wheel 188 and roller 194. Pipe 8 may then be threaded over the forward ends of ways 102, and on into the machine to the position shown in FIG. 1, the lower point of the pipe wall entering freely and passing between wheel 188 and roller 194. As the pipe is thus moved longitudinally, it is supported by roller wheels 78 along the length of the machine. After the pipe is inserted, post 116 may again be elevated to the solid line position of FIG. 1, wherein it supports ways I02, and fixture 176 removed. Since the fixture is disposed between ways 102, and the component posts 110 of compound post 116 are disposed outwardly of the ways, the fixture does not interfere with the raising or lowering of post 116.

Next, auxiliary frame 30 is elevated slightly so that wheels 76 carried thereby engage and lift pipe 8 out of engagement with rollers 78, and rollers 78 are lowered to their dotted line positon of FIG. 1 by operation of cylinder 96. The auxiliary frame 30 is lowered first to allow the pipe to rest on shear blades 22 of the lower rail, and further both to lower wheels 76 away from the pipe, and also to lower upper rail 28 so that its shear blades 22 clampingly engage the top of the pipe, as in FIGS. 9-12, and as previously described. Next, carrier 130 is swung back into place and secured by hook 142, pull beam 174 is advanced to bring ears 166 and 162 into registry, and pin 164 re-inserted to connect the pull beam to the cutter head. The cutter head is then pulled rearwardly to be supported by ways 102 rather than the carrier, but not so far as to cause cutter wheels 150 to enter the pipe. Carrier 130 is then again swung out of the way to the dotted line position of FIG. 4.

At this time, a second auxiliary fixture 200, forming the second of the two principal features of the present invention, and shown in FIG. 9-12, is inserted between upper and lower rails 28 and 20, forwardly of the forward end of the pipe, and forwardly of the cutter head. Said fixture includes a pair of upper parallel guide bars 202 which are horizontal and spaced apart to engage therebetween the shear blades 22 of the upper rail, and

a corresponding pair of lower guide bars 204 embracing the shear blades of the lower rail, and resting slidably on said lower rail. The upper and lower pairs of guide bars are each connected rigidly at their forward ends by a cross bar 206, said cross bars being spaced respectively below and above the associated shear blades, so as not to interfere therewith, and the upper and lower cross bars 206 are connected by a vertical handle 208 by means of which the fixture may be inserted and withdrawn. Just rearwardly of each cross bar 206, the associated guide bars 202 and 204 are also connected by a cross bar 210, each cross bar 210 projecting outwardly at both sides of ways 102, and each end of each of said cross bars having a tension spring 212 attached thereto. Said springs extend rearwardly and are attached, as at 214 (see FIG. 12) to some fixed part of the machine, such as guide posts 38 of the front bridge 12 of the main frame. Said springs bias the fixture rearwardly, but are easily detachable to permit removal of the fixture. Just rearwardly of cross bars 210, but still forwardly of the rearward ends of bars 202 and 204, the upper and lower bars 202 and 204 at one side of the shear blades are rigidly connected by a vertical post 216, and the bars 202 and 204 at the opposite side of the shear blades are similarly connected by a vertical post 218. Extending across the rearward sides of posts 216 and 218, forwardly of upper cutter wheel 150, is a horizontal arrester bar 220, and a similar arrester bar 222 is provided for the lower cutter wheel. Each ar rester bar is connected by a bolt 224 to a clamp bar 226 arranged across the forward edges of posts 216 and 218, so that by loosening said bolts, the arrester bars may be adjusted vertically on said posts. Each arrester bar has a vertical width corresponding to the space between adjacent teeth of the cutter wheels, so that it can enter therebetween. Guide bars 202 and 204 extend rearwardly from arrester bars 220 and 222 by a distance equal to the radius of each cutter wheel including its teeth. The fixture is adjusted by moving the arrester bars 220 and 222 vertically on posts 216 and 218, while engaged between adjacent teeth 154 of their associated cutter wheels, until the rearward end of one of the teeth of each wheel, this tooth being designated 154A in FIG. 10, is in the vertical plane of the rearward ends 228 of bars 202 and 204.

Next, the power drive of pull beam 174 is actuated to pull the cutter head rearwardly toward and into the pipe, arrester bars 220 and 222 being caused by springs 212 to follow the cutter head and secure the cutter wheels against rotation. When the rearward ends 228 of bars 202 and 204 engage the forward end of the pipe, rearward movement of fixture 200 is of course arrested, and at the same instant tooth 154A of each cutter wheel engages the end of the pipe, forcing the wheel to commence rotation. At this moment, the axis of the wheel is still spaced slightly forwardly of the pipe, which gives the next rearward tooth of the wheel further designated 154B in FIG. 10, ample clearance to enter the pipe. The arrester bar is then still engaged between the teeth, but the upper and lower edges of the arrester bars are rounded, as at 230, which permits the forced rotation of the wheel to cam the arrester bar forwardly against springs 212 momentarily. Thus tooth 154B cuts the first perforation, as already described, in spaced apart relation from the forward end of the pipe, as desired.

Rearward movement of the cutter head is continued to form a line of perforations along the top and bottom of the pipe along substantially the entire length thereof. However, movement of the cutter head is terminated short of the rearward end of the pipe to avoid possible cutting through the rearward end edge of the pipe, and pull beam 174 reversed to move the cutter head forwardly, with teeth 154 tracking in the perforations cut on the rearward pass. As tooth 154 emerges from the pipe, another tooth of the wheel will engage the arrester bar and force the fixture forwardly against springs 212 when the wheel axis is fiush with the forward end of the pipe, as shown in FIG. 9, since the arrester bar is not at that instant aligned with a tooth gap. This permits the wheel to continue turning till the head has moved slightly farther forwardly to the position of FIG. 10, thus clearing tooth 1548 from the last perforation, before springs 212 snap the arrester bar rearwardly into a tooth gap to arrest rotation of the wheel.

Forward movement of the cutter head is continued until it emerges from the pipe, pushing fixture 200 ahead of it. Then auxiliary frame 30 is elevated by cylinders 42 to first lift upper rail 28 free of the pipe and then to engage the pipe with rollers 76 and lift it free of lower rail 20. The pipe, then supported by rollers 76, is angularly indexed for another pass of the cutter head, the auxiliary frame lowered, and another double line of perforations cut as described above, the process being repeated until the entire pipe area is perforated. Each time the cutter head enters the pipe fixture 200 functions as described to insure repeated identical indexing of the cutter wheels. After perforation is completed, the pipe is removed by reversing the insertion procedure previously described, of course including the use of fixture 176 to support the forward ends of ways 102 as the pipe is withdrawn.

While we have shown and described specific embodiments of our invention, it will be readily apparent that many minor changes of structure and operation could be made without departing from the spirit of the invention.

What we claim as new and desire to protect by Letters Patent is:

l. The combination, with a pipe perforating machine wherein a pipe is clamped along diametrically opposite longitudinal lines between shear blades carried byrigid rails affixed to a machine frame, and perforated by the cutter teeth of a pair of cutter wheels, cooperating with said shear blades, as a cutter head in which said cutter wheels are rotatably mounted on axes transverse to said pipe, is moved longitudinally through said pipe, said cutter head being adapted to be moved into a first end of said pipe to a point adjacent its opposite end, then reversed whereby the teeth track in the perforations already formed until the head again emerges from said first end, said pipe being angularly rotated for subsequent passes of the cutter head, of guide means operable to support said cutter head at all stages of its movement, and to insure identical angular indexing of the cutter wheels each time said cutter head enters said pipe.

2. The combination as recited in claim 1 wherein said guide means includes:

a. a pair of elongated quide ways extending longitudinally through said pipe and outwardly from the ends thereof, said cutter head being slidably carried by said guide ways,

b. means rigidly affixing said guide ways to the machine frame adjacent said opposite end of said pipe, and

c. a fixture detachably connected to said guide ways adjacent said first pipe end, exteriorly of said pipe, and having a depending projection engageable at its lowermost portion with the lower of said shear blade rails, whereby to support said guide ways, the lower wall of said pipe being insertable between said rail and projection for threading of said pipe longitudinally over said guide ways.

3. The combination as recited in claim 2 wherein said fixture comprises:

a. a bracket, and

b. means operable to mount said bracket rigidly but removably on said guide ways, and wherein the depending projection of said fixture constitutes a roller wheel carried rotatably by said bracket on an axis transverse to said guide ways.

4. The combination as recited in claim 3 wherein said fixture additionally includes a second roller wheel carried removably by said lower shear blade rail for rotation on an axis parallel to said first roller wheel, and normally engaging said first roller wheel, whereby the pipe wall may be inserted beteeen and be longitudinally movable between said first and second roller wheels.

5. The combination as recited in claim 2 wherein said guide means additionally includes a rigid support member carried by the machine frame and movable from an operative position in which it engages and supports said guide ways adjacent said first pipe end, to an inoperative position in which it leaves the free ends of said guide ways unobstructed for the threading of a pipe thereover, said fixture being attachable to said guide ways out of the path of said rigid support member, so that it does not interfere with the movement of the latter between its operative and inoperative positions.

6. The combination as recited in claim I wherein said guide means includes a fixture operable to arrest and prevent rotation of said cutter wheels, relative to said cutter head, as said cutter wheels emerge from said first pipe end, whereby said cutter wheels enter into and emerge from said pipe with substantially equal angular indexing, relative to said cutter head, on all passes of said cutter head through said pipe.

7. The combination as recited in claim 6 wherein said fixture comprises:

a. a frame guided for movement longitudinally of said I pipe by said shear blade rails, and disposed outwardly of said first pipe end and said cutter head,

b. resilient means biasing said frame yieldably toward said first pipe end, and

c. a pair of arrester bars carried by said fixture frame,

each operable to engage between the teeth of one of said cutter wheels as the latter emerges from said first pipe end, and to be secured therebetween by said resilient means to arrest rotation of said cutter wheel, said resilient means permitting further outward movement of said fixture frame to permit said cutter head to be extended outwardly from said first pipe end.

8. The combination as recited in claim 7 wherein each of said arrester bars is operable to arrest the rotation of its associated cutter wheel at an angular index position of said cutter wheel in which the angular end of one of the teeth thereof directly confronts said first end of said pipe, whereby when the cutter head next enters said pipe, said tooth abuts said pipe and forces rotation of said cutter wheel.

9. The combination as recited in claim 8 wherein said fixture frame includes stop means engageable with said first pipe end to arrest the movement of said fixture frame toward said pipe end with said arrester bars spaced outwardly from said pipe end, whereby on emergence of the cutter head from the pipe, said arrester bars do not engage their associated cutter wheel teeth until said one tooth of each cutter wheel has completely emerged from said pipe, and the cutter wheel is 

1. The combination, with a pipe perforating machine wherein a pipe is clamped along diametrically opposite longitudinal Lines between shear blades carried by rigid rails affixed to a machine frame, and perforated by the cutter teeth of a pair of cutter wheels, cooperating with said shear blades, as a cutter head in which said cutter wheels are rotatably mounted on axes transverse to said pipe, is moved longitudinally through said pipe, said cutter head being adapted to be moved into a first end of said pipe to a point adjacent its opposite end, then reversed whereby the teeth track in the perforations already formed until the head again emerges from said first end, said pipe being angularly rotated for subsequent passes of the cutter head, of guide means operable to support said cutter head at all stages of its movement, and to insure identical angular indexing of the cutter wheels each time said cutter head enters said pipe.
 2. The combination as recited in claim 1 wherein said guide means includes: a. a pair of elongated quide ways extending longitudinally through said pipe and outwardly from the ends thereof, said cutter head being slidably carried by said guide ways, b. means rigidly affixing said guide ways to the machine frame adjacent said opposite end of said pipe, and c. a fixture detachably connected to said guide ways adjacent said first pipe end, exteriorly of said pipe, and having a depending projection engageable at its lowermost portion with the lower of said shear blade rails, whereby to support said guide ways, the lower wall of said pipe being insertable between said rail and projection for threading of said pipe longitudinally over said guide ways.
 3. The combination as recited in claim 2 wherein said fixture comprises: a. a bracket, and b. means operable to mount said bracket rigidly but removably on said guide ways, and wherein the depending projection of said fixture constitutes a roller wheel carried rotatably by said bracket on an axis transverse to said guide ways.
 4. The combination as recited in claim 3 wherein said fixture additionally includes a second roller wheel carried removably by said lower shear blade rail for rotation on an axis parallel to said first roller wheel, and normally engaging said first roller wheel, whereby the pipe wall may be inserted between and be longitudinally movable between said first and second roller wheels.
 5. The combination as recited in claim 2 wherein said guide means additionally includes a rigid support member carried by the machine frame and movable from an operative position in which it engages and supports said guide ways adjacent said first pipe end, to an inoperative position in which it leaves the free ends of said guide ways unobstructed for the threading of a pipe thereover, said fixture being attachable to said guide ways out of the path of said rigid support member, so that it does not interfere with the movement of the latter between its operative and inoperative positions.
 6. The combination as recited in claim 1 wherein said guide means includes a fixture operable to arrest and prevent rotation of said cutter wheels, relative to said cutter head, as said cutter wheels emerge from said first pipe end, whereby said cutter wheels enter into and emerge from said pipe with substantially equal angular indexing, relative to said cutter head, on all passes of said cutter head through said pipe.
 7. The combination as recited in claim 6 wherein said fixture comprises: a. a frame guided for movement longitudinally of said pipe by said shear blade rails, and disposed outwardly of said first pipe end and said cutter head, b. resilient means biasing said frame yieldably toward said first pipe end, and c. a pair of arrester bars carried by said fixture frame, each operable to engage between the teeth of one of said cutter wheels as the latter emerges from said first pipe end, and to be secured therebetween by said resilient means to arrest rotation of said cutter wheel, said resilient means permitting further outward movement of said fixture frame to permit said cutter heaD to be extended outwardly from said first pipe end.
 8. The combination as recited in claim 7 wherein each of said arrester bars is operable to arrest the rotation of its associated cutter wheel at an angular index position of said cutter wheel in which the angular end of one of the teeth thereof directly confronts said first end of said pipe, whereby when the cutter head next enters said pipe, said tooth abuts said pipe and forces rotation of said cutter wheel.
 9. The combination as recited in claim 8 wherein said fixture frame includes stop means engageable with said first pipe end to arrest the movement of said fixture frame toward said pipe end with said arrester bars spaced outwardly from said pipe end, whereby on emergence of the cutter head from the pipe, said arrester bars do not engage their associated cutter wheel teeth until said one tooth of each cutter wheel has completely emerged from said pipe, and the cutter wheel is in said index position.
 10. The combination as recited in claim 8 wherein the angular ends of said cutter wheel teeth, and also the effective edges of said arrester bars, are rounded about axes parallel to the cutter wheel axes, whereby the forced rotation of said cutter wheels operates to cam said arrester bars outwardly from engagement between the teeth of said wheels, against the bias of said resilient means. 